The present invention relates in general to cylinder type key locks and locking devices which are environmentally exposed, and more particularly to key operated rotary plug cylinder key locks having rotary disc type tumblers with special provisions to protect the key lock against jamming or faulty operation by dirt, grit, snow, or other foreign matter contaminants when used in possibly contaminated environment installations. A particularly useful application of the key operated cylinder lock is in padlocks designed for remote possibly contaminated environment use such as for locking railroad switches and security covers in remote, unsupervised locations.
One of the common types of key locks which have come into wide use is the type known as a cylinder lock. Conventional cylinder locks normally comprise a relatively fixed housing forming the lock body or casing having a cylindrical bore opening through the front surface of the lock body which rotatably houses a rotating cylinder or plug assembly. The rotatable cylinder or plug assembly has a keyway or key slot opening through the front surface of the cylinder or plug and extending over most of the axial length thereof, as well as one or more resiliently urged tumblers formed of rotatable or slideable members which normally occupy positions crossing the shear zones or interface zones at boundries between the rotatable cylinder core or plug and the outer body or shell preventing rotation of the core relative to the body or shell. When a key of proper contour or combination surfaces inserted in the keyway or key opening in the cylinder core or plug, the contoured key surface aligns the resiliently urged tumblers in such a way that a parting line, either of the tumbler members or of some other locking member coactive with the tumbler members, is brought into coincidence with the interface plane at the shear zone, or the locking member is withdrawn from interference in the path of the interface plane or peripheral surface of the core or plug, so that when all of the tumblers are properly aligned by the contoured key surface, rotational forces applied to the key permit the core or plug to turn through the normal motion involved in moving the lock, from a locked to an unlocked condition.
Heretofore, rotary disc tumbler cylinder key locks having a plurality of rotary disc tumblers provided with peripheral gates which, when properly aligned by the correct key with a locking rod or bar which normally spans across the shear zone between the rotary cylinder core and the housing or shell, of a type which may be desirable for use in padlock installations, have been disclosed in earlier U.S. Pat. Nos. 4,008,588 and 4,062,211 to Harry C. Miller et al and 4,083,212 assigned to the assignee of the present application. The disc tumbler key locks of Oy Watsila Ab U.S. Pat. Nos. 3,771,340 and 3,621,689 are of similar construction. However, due to the relatively close tolerances between relatively moveable parts frequently encountered in such cylinder locks, such padlocks are subject to contamination and possible jamming by small particulate foreign matter, snow, or other environmental contaminants when employed in possibly dirty or polluted environmental installations, such as railroad switch padlock applications and the like. Also, for many padlock applications, it is unnecessary to provide as many rotary disc tumblers as are provided in the cylinder locks disclosed in such earlier patents, and therefore flexibility in the choice of the number of disc tumblers, permitting easy selection during assembly of various numbers of rotary disc tumblers, is desired. Particular problems arise from infiltration of contaminants into the spaces between disc tumblers and into the key openings in the rotary disc tumblers in such applications, unless space is provided into which the contaminants can migrate out of positions where they would interfere with and induce jamming of the normal lock components.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.